This invention relates to glucose monitor systems and, in particular embodiments, to glucose sensors for use with glucose monitor systems and to the packaging for the glucose sensors. The invention also relates to the size, shape and positioning of electrodes on a glucose sensor.
Over the years, bodily characteristics have been determined by obtaining a sample of bodily fluid. For example, diabetics often test for blood glucose levels. Traditional blood glucose determinations have utilized a painful finger prick using a lancet to withdraw a small blood sample. This results in discomfort from the lancet as it contacts nerves in the subcutaneous tissue. The pain of lancing and the cumulative discomfort from multiple needle pricks is a strong reason why patients fail to comply with a medical testing regimen used to determine a change in characteristic over a period of time. Although non-invasive systems have been proposed, or are in development, none to date have been commercialized that are effective and provide accurate results. In addition, all of these systems are designed to provide data at discrete points and do not provide continuous data to show the variations in the characteristic between testing times.
A variety of implantable electrochemical sensors have been developed for detecting and/or quantifying specific agents or compositions in a patient""s blood. For instance, glucose sensors are being developed for use in obtaining an indication of blood glucose levels in a diabetic patient. Such readings are useful in monitoring and/or adjusting a treatment regimen which typically includes the regular administration of insulin to the patient. Thus, blood glucose readings improve medical therapies with semi-automated medication infusion pumps of the external type, as generally described in U.S. Pat. Nos. 4,562,751; 4,678,408; and 4,685,903; or automated implantable medication infusion pumps, as generally described in U.S. Pat. No. 4,573,994, which are herein incorporated by reference. Typical thin film sensors are described in commonly assigned U.S. Pat. Nos. 5,390,671; 5,391,250; 5,482,473; and 5,586,553 which are incorporated by reference herein. See also U.S. Pat. No. 5,299,571.
Many of these glucose sensors utilize complex chemical structures and/or reactions that can degrade over time, if maintained under improper conditions. Since sensors may be stored for long periods of time after manufacture and prior to use, the sensors must be monitored frequently and maintained in areas with a carefully controlled environment. The monitoring of sensors is particularly difficult once the sensors have been sterilized and placed in packages. Often the only way to monitor the sensors is to pull a sample and remove it from a package. However, this destroys the sterility and results in waste. Also, monitoring sensors that have been shipped to a user are problematic or difficult.
It is an object of an embodiment of the present invention to provide an improved glucose sensor package system, which obviates for practical purposes, the above mentioned limitations.
Embodiments of the present invention are directed to a glucose sensor package system that includes a glucose sensor and a protective package that indicates proper exposure to sterilization or exposure to temperature changes to indicate proper temperature control. Also covered are methods of transporting and sterilizing the package. In addition, further embodiments of the glucose sensors are directed to the sizing and positioning of the electrodes on the glucose sensor.
According to an embodiment of the invention, a glucose sensor package system for storing and transporting a glucose sensor includes at least one glucose sensor, a protective package and at least one temperature exposure indicator. The protective package has an interior to hold the at least one glucose sensor in the interior of the protective package. The at least one temperature exposure indicator is used to determine if the protective package has been exposed to at least one exposure temperature relative to a predetermined threshold temperature value. In particular embodiments, the at least one exposure temperature is above the predetermined threshold temperature, and the at least one temperature exposure indicator indicates when there has been exposure to the at least one exposure temperature. For instance, the predetermined threshold temperature is 75xc2x0 F. and the at least one exposure temperature exceeds 75xc2x0 F., or the predetermined threshold temperature is 100xc2x0 F. and the at least one exposure temperature exceeds 100xc2x0 F. In other embodiments, the at least one exposure temperature is below the predetermined threshold temperature, and the at least one temperature exposure indicator indicates when there has been exposure to the at least one exposure temperature. For instance, the predetermined threshold temperature is 36xc2x0 F. and the at least one exposure temperature is below 36xc2x0 F.
In additional embodiments, the at least one temperature exposure indicator indicates when the at least one exposure temperature relative to the predetermined threshold temperature existed for a predetermined period of time. For instance, the predetermined period of time can be at least 10 minutes, or at least 60 minutes. In other embodiments, the period of time is established as a function of a magnitude of a difference between the at least one exposure temperature and the predetermined threshold temperature.
In particular embodiments, the at least one temperature exposure indicator is attached to the protective package. For instance, the at least one temperature exposure indicator may be attached to the interior of the protective package or an exterior of the protective package. In further embodiments, the at least one temperature exposure indicator is contained within the protective package, or attached to the glucose sensor. In preferred embodiments, the at least one temperature exposure indicator is a sticker. Other embodiments are directed to a method of transporting the glucose sensor in a package system.
According to another embodiment of the invention, a glucose sensor package system for storing and transporting a glucose sensor includes at least one glucose sensor, a protective package, and at least one temperature exposure indicator. The protective package has an interior within which the at least one glucose sensor is disposed, and an exterior. The at least one temperature exposure indicator has first and second states, of which the first state indicates that the protective package has not been exposed to at least one exposure temperature relative to a predetermined threshold temperature value, and the second state indicates that the protective package has been exposed to the at least one exposure temperature. The at least one temperature exposure indicator, in particular embodiments, is attached to the interior of the protective package or the exterior of the protective package, is contained within the protective package, or is attached to the glucose sensor.
In further particular embodiments, the glucose sensor package system includes a plurality of glucose sensors, each of which is enclosed within a separate package. The plurality of separately packaged glucose sensors in turn are disposed within the interior of the protective package. In more specific embodiments, the glucose sensor package system includes a plurality of the at least one temperature exposure indicators, each of which is attached to one of the separate packages.
In further embodiments, the glucose sensor package system includes a plurality of the at least one temperature exposure indicators, each of which provides an indication of exposure to at least one exposure temperature relative to a different predetermined threshold temperature value. These embodiments afford more precise indications of a maximum temperature to which the package system has been exposed.
Another embodiment of the present invention is directed to a method of transporting a glucose sensor. The method includes the steps of providing at least one glucose sensor. Providing a protective package having an interior. Holding the at least one glucose sensor in the interior of the protective package. Using at least one temperature exposure indicator to determine if the protective package has been exposed to at least one exposure temperature relative to a predetermined threshold temperature value.
A further embodiment of the present invention is directed to a method of transporting a glucose sensor, the method including the steps of providing a glucose sensor package system. The package system including at least one glucose sensor, a protective package having an interior within which the at least one glucose sensor is disposed and an exterior, and at least one temperature exposure indicator having first and second states. Transporting the glucose sensor package system, and observing the state of the at least one temperature exposure indicator to determine if the protective package has been exposed to the at least one exposure temperature during transport.
Additional embodiments of the method employ a glucose sensor package system that includes a plurality of the at least one temperature exposure indicators, each of which provides an indication of exposure to at least one exposure temperature relative to a different predetermined threshold temperature value. In these embodiments, the observing step includes an observation of the state of each of the at least one temperature exposure indicators to determine if the protective package has been exposed to at least one exposure temperature relative to at least one of the different predetermined threshold values.
Another embodiment of the present invention is directed to a glucose sensor package system for sterilizing a glucose sensor using electron beam sterilization, the system including at least one glucose sensor, a protective package, and at least one radiation exposure indicator. The protective package has an interior to hold the at least one glucose sensor in the interior of the protective package. The at least one radiation exposure indicator is used to determine if the protective package has been exposed to a predetermined exposure level of electron beam sterilization. For example, preferred embodiments have the predetermined exposure level above 2.0 Mrad. Other embodiments have the predetermined exposure level less than or equal to 5.0 Mrad or above 0.5 Mrad. In further embodiments, the at least one radiation exposure indicator indicates that the predetermined exposure level existed for a period of time.
In particular embodiments, the at least one radiation exposure indicator is attached to the protective package. For example, the at least one radiation exposure indicator may be attached to the interior of the protective package, or an exterior of the protective package. In other embodiments, the at least one radiation exposure indicator may be contained within the protective package. In further embodiments, the radiation exposure indicator may be attached to the glucose sensor. Preferably, the at least one radiation exposure indicator is a sticker. Other embodiments are directed to a method of sterilizing the glucose sensor.
Still additional embodiments are directed to a glucose sensor including a substrate, a working electrode including at least one enzyme and being coupled to the substrate, a counter electrode coupled to the substrate, and a reference electrode coupled to the substrate. In preferred embodiments, the counter electrode is formed larger than the working electrode, and the working electrode is formed larger than the reference electrode. In still further embodiments, the working electrode is placed between counter electrode and the reference electrode. In additional embodiments, the glucose sensor also includes at least one attached temperature exposure indicator.
Packaged glucose sensors as described above are also provided in accordance with further embodiments. Further embodiments include at least one temperature exposure indicator attached to the packaging and/or to the glucose sensor.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention.